Store result of function in a global variable

Question

I'm new at learning javascript. I am trying to create a function that calculates something, and then stores the end result of the calculation in a global variable.

I am clearly doing something wrong because it is writing the entire code of the function to the document, instead of just writing the result.

 var myNumbers = function myCalculation () {
        var myCalc1 = 4 + 6;
        var myCalc2 = myCalc1 + 100;
        var myCalc3 = myCalc2 + 20;
        return myCalc3
}

document.write(myNumbers);

Answer 1

myNumbers is a reference to a function, not the result of the call to that function.

I think you mean:

function myCalculation () {
        var myCalc1 = 4 + 6;
        var myCalc2 = myCalc1 + 100;
        var myCalc3 = myCalc2 + 20;
        return myCalc3
}

var myNumbers = myCalculation();

document.write(myNumbers);

What is the difference between a function call and function reference?

Answer 2

You can do this various ways. But, first you must understand the ways of defining functions in javascript. I am providing two ways here. For more read this and this.

1. The regular way:

function add(a, b) {
  let c = a + b;
  return c;
}

2. The function expression way:

let add = function(a, b) {
  let c = a + b;
  return c;
}

You can use any of them declare a function, though there's some difference in them. But, for your usecase, it won't be problem.

So, you can declare myCalculation as follows:

function myCalculation () {
    var myCalc1 = 4 + 6;
    var myCalc2 = myCalc1 + 100;
    var myCalc3 = myCalc2 + 20;
    return myCalc3;
}

or

let myCalculation = function() {
    var myCalc1 = 4 + 6;
    var myCalc2 = myCalc1 + 100;
    var myCalc3 = myCalc2 + 20;
    return myCalc3;
}

Then, you can do:

let myNumbers = myCalculation();
document.write(myNumbers);

And again there's another way, you can do this without creating myCalculation function, by using immediate call to anonymous function(note: this is created using function expression, read the links I've provided):

let myNumbers = (function myCalculation() {
    var myCalc1 = 4 + 6;
    var myCalc2 = myCalc1 + 100;
    var myCalc3 = myCalc2 + 20;
    return myCalc3;
})();

// and then
document.write(myNumbers);

You should whatever fits your situation...

Answer 3

End result store by calling the myCalculation() and result automatically store in the global variable.

var myNumbers = myCalculation();

function myCalculation () {
    var myCalc1 = 4 + 6;
    var myCalc2 = myCalc1 + 100;
    var myCalc3 = myCalc2 + 20;
    return myCalc3
}

document.write(myNumbers);